Re: Amplify the hell out of it.

From: John Popelish (jpopelish_at_rica.net)
Date: 02/26/05 

Date: Fri, 25 Feb 2005 22:23:01 -0500

"Gregory L. Hansen" wrote:
>
> In article <4216219E.E375B008@rica.net>,
> John Popelish <jpopelish@rica.net> wrote:

> >I also emailed the seller and verified that this interpretation is
> >correct. After you have yours on the way, I may order one to play
> >with.
>
> Somehow it seems bigger than it looked in the pictures. The can is five
> inches in diameter, almost three inches high, the sensors mounted on the
> lid which has two arrows oriented with the two horizontal sensors and a
> spirit level in the middle. The large screws (5/16"?) on the bottom allow
> mounting to something. And the two fittings are rubberized compression
> seals that would allow wiring through conduit.
>
> I haven't had the chance to plug it in to anything yet, but from the
> physical inspection I like it.

Thanks for the report. That is about how big I expected it to be.
But since talking with you, I have sort of gotten my heart set on
making my own sensor coils and an Lehman type long period
seismometer. I have a bunch of magnets selected for purchase, and am
getting a quote from a machinist tomorrow, for the iron pole pieces.
I think I can achieve quite a multiple of the signal to noise ratio
(50, perhaps) compared to any sensors I have seen that hobbyists
build. It has a hum bucking coil design that cancels the effect of
large fields, like power line hum, lightning and variations in the
geofield caused by aurora. And the whole coil sits in an
approximately 10,000 gauss field. It would make one hell of a linear
motor.

My goal is to be able to lie down on the concrete, next to my unit,
and monitor my heart beat above the noise. If it will do that, I
should be able to pick up any significant quake on the planet. Like
the geophone pickups, this will be a velocity output.

If I get that to work, I want to add an optical detector that goes
down to DC so the unit effectively becomes a tilt meter. I have no
idea how sensitive I can make that, compared to the magnetic unit.
Connecting them in a feedback loop, to hold the magnetic bob
stationary with respect to the Earth will make the coil current
proportional to acceleration.

I am very interested to hear how your amplifier works with the unit
you have purchased. I need to get a few of those LT1007 opamps for
the front end of mine.

After you get a signal, I would like to talk with you about filtering
possibilities to reduce high frequency (road traffic) noise and extend
the low frequency performance, if these things interest you. 

-- 
John Popelish

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